ADDITIONAL OBSERVATIONS ON VARIATIONS IN EGG SIZE AMONG POPULATIONS OF STREPTOCEPHALUS SEALI (ANOSTRACA)

Abstract

We evaluated the interrelationships between egg size, maternal length, and habitat type for the fairy shrimp Streptocephalus seali from a variety of localities. Our analyses demonstrated a correlation between female length and egg size for samples from California, Florida, and Montana, and for pooled data using all samples. However, there was no such correlation for the sample from Louisiana. The regression between egg size and female length for meltpool populations that generally produce larger eggs is significantly different from the regression for the rainpool populations that typically form smaller eggs. Belk (1977) first observed this difference in egg size between meltpool and rainpool populations in a comparison of S. seali from Arizona and Louisiana. We confirmed this difference and extended it to include samples from Alabama, California, Florida, Montana, North Carolina, and Chiapas, Mexico. Other factors demonstrated to significantly affect egg size are habitat latitude, habitat altitude, and the interactive effects of the independent variables evaluated. We concluded that egg-size variations between populations of S. seali inhabiting rainpools and meltpools reveal evolutionary responses to differing ecological situations.